1. Field of Invention
This invention relates to an apparatus for varying the compression ratio of an internal combustion engine while running.
2. Description of Prior Art
The efficiency of an internal combustion engine is related to its compression ratio. The selection of too low a ratio reduces power and efficiency. The selection of too high a ratio increases octane requirements and eventually causes knocking with its accompanying power loss and possibility of engine damage. The ability to adjust the compression ratio while the engine is running permits the engine to be operated with improved efficiency over a wide throttle range, with a wide octane range and, in the case of turbocharged or supercharged engines, with higher boost than could normally be used.
Although many patents have been filed in this area there appear to be no commercially successful designs. Some patents use the rotating eccentric bearing method (between the piston pin and connecting rod) to vary the compression ratio by raising or lowering the piston on the connecting rod. Most of these rely on the fact that there are upward and downward inertia and gas pressure forces on the piston which can be used to rotate the bearing to a new position.
The following patents are typical of those based on using the forces on the piston to rotate an eccentric bearing with hydraulically driven locking pins to engage a high or low position: U.S. Pat. No. 4,687,348 dated Aug. 18, 1987 and titled DEVICE FOR LOCKING/UNLOCKING ROTATION OF AN ECCENTRIC BEARING USED IN A COMPRESSION RATIO CHANGING MECHANISM OF AN INTERNAL COMBUSTION ENGINE; U.S. Pat. No. 4,721,073 dated Jan. 26, 1988 and titled COMPRESSION RATIO CHANGING DEVICE USING AN ECCENTRIC BEARING FOR AN INTERNAL COMBUSTION ENGINE; U.S. Pat. No. 4,830,517 dated May 16, 1989 and titled DEVICE FOR LOCKING ROTATION OF AN ECCENTRIC BEARING OF A COMPRESSION RATIO CHANGING DEVICE; U.S. Pat. No. 4,864,975 dated Sep. 12, 1989 and titled COMPRESSION RATIO CHANGING DEVICE FOR INTERNAL COMBUSTION ENGINE. While all of the above patents are based on hydraulically driven locking pins, the first three listed deal specifically with the problems of high impact, deformation and reliability due to partial engagement of the pins when changing from one locking position to another.